Study On Instability Mechanism And Surrounding Rock Control Technology Of Gob-side Entry Retaining Combined Backfill In Fully Mechanized Caving Face

As a pillar-free mining technology,gob-side entry retaining has unparalleled advantages in improving the recovery rate of coal resources,reducing the amount of roadway excavation,and optimizing the ventilation of the working face.It is an important direction for green mining and scientific development in the coal industry..At present,gob-side entry retaining filling materials are mainly divided into rigid materials and flexible materials.The former has poor roof connection and compressibility.Under high stress,it is easy to cause shear failure of the roof and floor in the roadway or cracking and instability of the wall.The latter is under high stress.It is not easy to control the lateral displacement of the wall,resulting in large deformation of the filling body.For gob-side entry retention in high-gas mines under complex conditions,the roadside support should have the properties of closed goaf,initial support force,flexible yielding pressure,and key bearing capacity.Gob-side entry retaining combined filling technology is an effective way to solve the above problems.By constructing gob-side entry retaining combined structure filling body,a "strongflexible" combined structure is formed to meet the stress and deformation requirements of roadside support.After consulting a large number of literatures,there are few reports on the combined filling technology of gob-side entry retaining.This thesis comprehensively uses theoretical analysis,laboratory experiments,numerical simulation,field tests and other means to carry out research on the instability mechanism of gob-side entry retaining combined backfill body and surrounding rock control technology in fully mechanized caving face,and build a mechanical model of combined structure backfill body and roof.Carry out research on layered material optimization and mechanical properties of combined structure backfill,reveal the instability mechanism of gob-side entry retaining combined structure backfill,establish a surrounding rock control technology system with "gob-side entry combined backfill technology" as the core,and optimize roadway support Parameters and forms,the main research results and conclusions are as follows:(1)Tests on mechanical parameters of surrounding rock of working face were carried out to summarize the deformation and failure characteristics of surrounding rock of single structure filling body along goaf retaining,and reveal the failure mechanism of single structure filling body of stress concentration type,strength deficiency type and roof and floor shear type,Proposed the concept of " combined filling with goaf retaining roadway",detailed elaborated along the combination for filling technology principle,structure features and key technology,namely the upper support flexible material was used to construct stress on good form,the thickness of thin,compressible let top pressure,the lower part of the rigid materials build resistance to deformation ability,large bearing capacity of high-strength load-bearing layer.(2)Based on the structural characteristics of the composite structure backfill body,a mechanical model of the interaction between the composite structure backfill body and the roof at the breaking critical point of the basic arc-shaped triangular block and the gangue balance is established.strength and thickness equation expressions,discuss the variation law of delamination strength and delamination thickness of composite structure backfill with structural parameters,and give the applicability criterion of gobretention combined backfill technology.(3)Ratio of layered composite structure filling body material optimization and research,to under different intensity of layered materials,high layered and layered composite sample mechanics performance test research,layering key analysis,high ratio and strength the influence law of mechanical properties of composite were investigated,offer different layered composite sample deformation under high ratio and stratified intensity,the macro fracture morphology and failure characteristics of acoustic emission technology was used to study the influence of interface effect on the crack initiation and propagation law of the composite sample,and the reasonable recommended values of delamination materials and parameters of the filling body with goaf retaining structure were given.(4)Based on assembly sample mechanics performance test results,the FLAC3 D numerical simulation method to simulate different layered composite structure filling body strength,layer thickness and filling body under the width of the roadway surrounding rock stress field,displacement field and plastic zone evolution law,further determine the combination structure of filling body structure parameters,mechanism to reveal the combination structure of filling body stability,It provides reference and theoretical basis for the reasonable selection and scheme design of roadway side support parameters.(5)Put forward the "asymmetric control together-combination packing-unloading" trinity,surrounding rock control technology in detail elaborates the characteristics,the control principle and supporting and support from the zone control,multi-level support,lane cooperative shape-shifting perspective,such as combination for filling along gob area is given surrounding rock control technology system,optimization of 2603 transport roadway supporting method and parameters,FLAC3 D was used to simulate the prestress,displacement field and plastic zone distribution of roadway without support,symmetric support and asymmetric support to verify the reliability of the support scheme.(6)The combined filling technology of gob-side roadway retention was studied and the combined filling process was designed.The combined filling technology and asymmetric support scheme were applied to the 2603 working face of Zhangcun Coal Mine.Monitoring means such as cross point method,surrounding rock drilling peeping,force meter,rebound meter and gas meter were adopted.The dynamic monitoring and evaluation of surrounding rock surface displacement,roof separation layer and deep surrounding rock deformation,anchor cable load,filling body strength and roadway gas concentration were carried out.The monitoring results show that the field application effect is good.The thesis has 122 figures,41 tables,and 161 references.